Effects of fasting on the composition of gallbladder bile.

Gallbladder bile was aspirated from the duodenum in nine healthy women after three separate periods of fasting after a standardised meal. Mean cholesterol saturation index was significantly greater after a 15 hour fast (1.35 +/- 0.08) than after a 10 hour fast (1.05 +/- 0.10). However, after 20 hours of fasting, mean cholesterol saturation index had fallen to 1.13 +/- 0.10. Total biliary lipid concentration was unaffected. These findings suggest that fasting has a series of effects on gallbladder bile and that bile sampling should be carried out at at standardised period of time after the last meal.